It is common for enterprises to use network storage systems, such as Storage Area Networks (SANs) and Network Attached Storage (NAS). One common arrangement is for an enterprise to use one or more Redundant Arrays of Independent Disks (RAIDs) to store data in a manner that is reliable and easy to access.
Such systems provide virtual storage volumes for access by host devices. For instance, a user at a computer (e.g., a host) may want to access a file stored to a network. The host computer sees a number of drives on the network, where the drives are provided by the storage system and may or may not correspond to physical disk drives. One or more storage controllers at the storage system organize the various storage resources (e.g., hard disk drives, solid state drives, etc.) into a number of virtual drives, where the complexity of virtualizing and managing the physical storage resources is not seen by the host.
Some network storage systems include many hosts accessing a number of virtual volumes provided by one or more storage controllers. A given volume may have only one or two paths for access, meaning that only one or two access requests may be made to the volume at a given time. In other words, a given volume may be limited in the number of accesses it can handle at any one time.
In order to make read access more efficient, some conventional systems provide for mirror volumes. Mirror volumes in this example include duplicates of the original (or source) volume, and the are accessible independently of the original volume. Thus, adding a single mirror volume may double the number of paths available to read the data held by the source volume. Similarly, adding two mirror volumes may triple the number of paths to access the same data.
Such conventional systems use processing resources to generate and update the mirror volumes. Furthermore, each minor volume takes up space on the physical storage resources. Therefore, it may be advantageous in some systems to generate smaller mirror volumes to save processing resources and available storage space in the storage system.